Transducers for perpendicular recording with write pole tip angled toward media

ABSTRACT

A write pole tip for a magnetic head has a trailing edge that is closer than a leading edge to a perpendicular recording medium, so that the write signal strength of the trailing edge is greater than that of the leading edge. Such an angled pole tip can write a sharp magnetic pattern with the trailing edge, reducing erroneous writing. A layer of physically hard material such as diamond-like carbon (DLC) may adjoin the trailing edge, the physically hard material layer protruding slightly after polishing of the media-facing surface due to its resistance to lapping. This can form an acute corner of the write pole tip adjacent to the physically hard material layer. The trailing edge may be longer than the leading edge, and the write pole tip may have a trapezoidal shape.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §120 of (is acontinuation of) application Ser. No. 10/902,673, filed Jul. 29, 2004,now U.S. Pat. No. 7,508,624, which in turn claims the benefit under 35U.S.C. §119(e) of provisional application Ser. No. 60/491,708, filedAug. 1, 2003, both of which are by the same inventor and areincorporated by reference.

SUMMARY

In one embodiment a write pole tip is disclosed having a trailing edgethat is closer than a leading edge to a perpendicular recording medium,so that the write signal strength of the trailing edge is greater thanthat of the leading edge. Such an angled pole tip can write a sharpmagnetic pattern with the trailing edge, reducing erroneous writing. Alayer of physically hard material such as diamond-like carbon (DLC) mayadjoin the trailing edge, the physically hard material layer protrudingslightly after polishing of the media-facing surface due to itsresistance to lapping. This can form an acute corner of the write poletip adjacent to the physically hard material layer.

In one embodiment a write pole tip is disclosed having a trailing layerthat is closer than a leading layer to a perpendicular recording medium,with a physically hard material layer adjoining a leading edge and atrailing edge of the trailing layer. In one embodiment a physically hardmaterial layer can serve as a nonconducting laminate disposed betweenthe leading layer and the trailing layer to reduce eddy currents. In oneembodiment at least one physically hard material layer can also adjoin asensor so that the sensor also protrudes slightly toward the recordingmedium.

In one embodiment a material that is physically softer than the pole tipmaterial can adjoin the leading edge of the write pole, the physicallysofter material being recessed at the media-facing surface relative tothe pole tip and causing the leading corner of the pole tip to have anobtuse angle. In one embodiment, a first material that is physicallyharder than the pole tip material can adjoin the trailing edge of thewrite pole and a second material that is physically softer than the poletip material can adjoin the leading edge of the write pole, accentuatingthe slope of the pole tip relative to the media. In one embodiment, afirst material that is physically harder than the pole tip material canadjoin the trailing edge of the write pole and softer material canadjoin the leading edge and both sides of the write pole, accentuatingthe slope of the pole tip and reducing side writing when the pole tip isskewed relative to a medium track.

In one embodiment the write pole tip may have a trailing edge that islonger than its leading edge, which helps to reduce side writing. Forexample, by using the physically hard material that adjoins the trailingedge as an etching mask, an angled IBE can create a write pole tiphaving a substantially trapezoidal shape. In one embodiment, anauxiliary pole tip can be formed that is separated from the write poletip by a submicron layer of physically hard material, the auxiliary poletip deflecting the write flux from the write pole tip to an angle fromperpendicular to facilitate rotation of the media layer bits. In analternative embodiment, the return pole tip can be separated from thewrite pole tip by a submicron layer of physically hard material, thereturn pole tip deflecting the write flux from the write pole tip to anangle from perpendicular to facilitate rotation of the media layer bits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway cross-sectional view of a first embodiment of anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

FIG. 2 is a cutaway cross-sectional view of a second embodiment anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

FIG. 3 is a cutaway cross-sectional view of a third embodiment of anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

FIG. 4 is a cutaway cross-sectional view of a fourth embodiment anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

FIG. 5 is a cutaway cross-sectional view of a stage in the fabricationof a transducer similar to that shown in FIG. 3.

FIG. 6 is a cutaway cross-sectional view of a later step in thefabrication of the transducer shown in FIG. 5.

FIG. 7 is a cutaway cross-sectional view of a later step in thefabrication of the transducer of FIG. 6.

FIG. 8 is a cutaway cross-sectional view of a later step in thefabrication of the transducer of FIG. 7.

FIG. 9 is a cutaway cross-sectional view of a fifth embodiment anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

FIG. 10 is a cutaway cross-sectional view of a sixth embodiment anelectromagnetic transducer designed for writing and reading informationon a medium such as a rigid disk.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of an electromagnetic transducer 20designed for writing and reading information on a medium 21 such as arigid disk. The transducer 20 is part of a larger body that may betermed a head or slider, which has a media-facing surface 22, a trailingend 24 and a leading end that is not shown in this figure. The medium 21is moving relative to transducer 20 in a direction shown by arrow 19.

Transducer 20 has been formed in a number of thin layers along withthousands of similar transducers on a wafer substrate 30, which may bemade of various materials known in the industry, such asalumina-titanium-carbide. The substrate 30 and attached layers were thencut into individual heads that were worked to form surfaces such asmedia-facing surface 22. A first low coercivity, high permeability (softmagnetic) shield layer 35 has been formed on the substrate or a seedlayer, not shown, followed by a magnetoresistive (MR) sensor 33 and asecond soft magnetic shield 37. The MR sensor can be any transducer thatsenses a magnetic field with electrical resistance or conductivity, suchas a spin valve sensor, spin-dependent tunneling sensor, giant MRsensor, etc. Nonmagnetic, electrically insulating material 38 such asalumina is disposed between the shields and adjacent to the MR sensor33.

A first pole layer 40 of soft magnetic material such as permalloy isseparated from shield 37 by additional insulating material, andterminates in a media-facing first pole tip 42. The first pole layer 40is magnetically coupled to a second soft magnetic pole layer 44 by asoft magnetic stud 45. The second soft magnetic pole layer 44 terminatesin a media-facing second pole tip 46. While the first pole layer 40 canbe seen to be thicker than the second pole layer 44, the first polelayer 40 is also much wider than the second pole layer 44 in a dimensionperpendicular to the cross-section shown in FIG. 1, and the area offirst pole tip 42 is much greater than that of second pole tip 46. Dueto the higher concentration of flux passing through the second polelayer 44 and the second pole tip 46, those elements may be termed therecording pole layer and tip, respectively. The recording pole layer 44or a trailing layer of the recording pole layer may be made of a highmagnetic saturation (high B_(SAT)) material such as a predominantly-ironnickel-iron alloy (e.g., Ni₄₅Fe₅₅), CoZrTa, predominantly-iron FeN orFeNX, where X is Al, Rh, etc.

A first coil layer 50 has plural sections that wind between pole layers40 and 44, and is connected to a second coil layer 52 that winds in anopposite direction, so that the magnetic field from coil layers 50 and52 add constructively in the area of pole layer 44, causing a magneticfield in that pole layer to be directed toward or away from the medium21.

A layer 55 of physically hard material (e.g., DLC, silicon-carbide(SiC), tetrahedral amorphous carbide (ta-C), diamond (C), boron-carbide(B₄C), boron-nitride (BN) or other insulating materials that are harderthan alumina) adjoins a trailing edge 57 of second pole layer 44.Insulating material 58 such as alumina has been formed atop the secondcoil layer 52, and other insulating material such as baked photoresistmay be disposed between the sections of that layer 52. The greaterhardness of layer 55 causes that layer to protrude at the media-facingsurface 22 compared to other layers, because layer 55 had greaterresistance to lapping and polishing that was used to form themedia-facing surface 22. A trailing corner 60 of the second pole tip 46forms an acute angle near the hard layer 55. After lapping andpolishing, an overcoat 62 has been formed on the transducer 20 toprotect it from wear and corrosion, the overcoat made of physically hardmaterial such as DLC, SiC or ta-C.

The medium 21 in this embodiment is a disk having a self-supportingsubstrate 70 of inflexible material such as aluminum or glass, overwhich a soft magnetic underlayer 72 has been formed. A high coercivitymedia layer 74 is disposed over the underlayer 72 and beneath a diskovercoat 76. The media layer 74 may have an easy axis of magnetizationthat is substantially perpendicular to a surface 78 of the medium 21,and may be formed of a plurality of layers, such as magnetic alloylayers separated by a nonmagnetic metal layer, with a fine grainedcrystalline structure to reduce noise. The soft magnetic underlayer 72can form a magnetic circuit with the soft magnetic layers 40, 44 and 45of the transducer 20, the magnetic flux of the circuit traversing themedia layer 74 for writing to the medium 21. Because of the largedifference in area disposed proximate to the medium 21 of the first poletip 42 compared to the second pole tip 46, the second pole tip 46 maycommunicate concentrated magnetic flux sufficient to write a signal onthe media layer 74 whereas the first pole tip 42 communicates dispersedmagnetic flux insufficient to write a signal on the media layer 74. Forexample, the first pole tip may have an area that is at least two orthree orders of magnitude greater than that of the second pole tip.

The media-facing surface 22 of the head is shown operating in contactwith the disk surface adjacent to trailing corner 60 but may also floatless than 100 Å above the disk surface. The media-facing surface 22 mayprotrude adjacent to trailing corner 60 by between a few angstroms andabout 100 Å, depending on various factors including the relative sizeand hardness of layers 55 and 44. The magnetic signal strength at themedium layer 74 from pole tip 46 depends greatly on the distance betweenthe pole tip 46 and the medium layer 74. For a contact recordingembodiment in which the combined thickness of transducer overcoat 62 anddisk overcoat 76 is less than 100 Å, forming recording 46 pole tip tohave a leading edge 48 that is 100 Å further than trailing edge 57 fromthe media layer 74 can produce dramatically stronger signal strength atthe trailing corner 60, which may write to the media while the leadingedge 48 of pole tip 46 does not.

The thickness of hard layer 55 may be in a range between about 100 Å andabout 1 μm, and its width (measured in a direction perpendicular to thecross-section of FIG. 1) may be within a similar range of values. In oneembodiment, the width of hard layer 55 may be substantially equal to thewidth of the trailing corner 60, which defines the width of a trackwritten by the pole 46. In that case, the width of the hard layer 55 andthat of the trailing pole layer 44 may both be defined by directedetching such as ion beam etching (IBE) or reactive ion etching (RIE). Inaddition to the materials mentioned above, other materials that may beused for hard layer 55 include diamond (C), boron (B), boron-nitride(BN), boron carbide (B₄C), and aluminum boride (AlB₁₂), all of whichhave a Vickers hardness (HV) greater than that of alumina (Al₂O₃).

In FIG. 2 an optional, relatively soft material layer 80 is disposedbetween the pole tips 42 and 46. The layer 80 is physically softer thanalumina and so has been removed during lapping and polishing at agreater rate than the alumina insulating layers, forming a recess in themedia-facing surface adjacent to pole tip 46. This can cause the leadingedge 48 of pole tip 46 to be further removed from the media than wouldotherwise be the case, so that less signal is transmitted to the mediumfrom the leading edge of that pole tip, amplifying the signal written bythe trailing edge. Examples of materials that can be used to form thesoft material layer 80 include aluminum nitride (AlN), silicon nitride(Si₃N₄), silicon dioxide (SiO₂), titanium oxide (TiO₂), zirconiumoxide(ZrO₂), hafnium oxide(HfO₂), thorium oxide(ThO₂), berylliumoxide(BeO) and magnesium oxide (MgO). Note that these materials are notelectrically conductive.

Such a softer material can also be optionally disposed on both sides ofthe pole tip 46, so that the sides of the pole tip 46 are furtherrecessed compared to the trailing corner 60. This can help to reduce offtrack writing. A softer material has also been formed in a layer 82disposed between the substrate and the first shield 35, as well as in alayer 84 disposed between the second shield layer 37 and the first polelayer 40, so that those areas of the media-facing surface 22 arerecessed from that adjacent to the recording pole corner 60. Arelatively hard material such as DLC, to-C, SiC or the like has beenformed in at least one layer disposed between the first shield 35 andthe second shield layer 37 in the area shown generally as 38, which hascaused the media-facing surface 22 to protrude slightly adjacent to theMR sensor.

FIG. 3 shows an embodiment that has plural recording pole layers 90 and92, layer 92 terminating in recording pole tip 94 while layer 90terminates between a few nanometers and a few microns further away fromthe media-facing surface 22. Pole layer 92 may be formed of physicalvapor deposited (PVD), high moment material (e.g., B_(sat) greater than20 kiloGauss). The thickness of pole layer 92 may be in a range betweenabout 10 Å and 1000 Å, and its width (measured in a directionperpendicular to the cross-section of FIG. 1) may be within a similarrange of values. In one embodiment, the width, of pole tip 94 may be atleast three times the thickness of that pole tip to reduce off trackwriting. The thickness of hard layer 55 may be in a range between about100 Å and about 1 μm, and its width (measured in a directionperpendicular to the cross-section of FIG. 1) may be within a similarrange of values. In one embodiment, the width of hard layer 55 may besubstantially equal to the width of the pole layer 92, which defines thewidth of a track written by the pole tip 94. In that case, the width ofthe hard layer 55 and that of the trailing pole layer 92 may both bedefined by masking and etching by IBE, RIE or the like.

FIG. 4 shows an embodiment that has a relatively hard layer 95 such asDLC, ta-C, SiC, BN or the like disposed adjacent to pole layer 94,between pole layer 90 and the hard overcoat 60. Recording pole tip 94 inthis case has hard material adjacent to its leading edge and itstrailing edge, and can be formed with alumina on the sides of layer 92.Alternatively, a material that is harder or softer than alumina can bedisposed on either or both sides of pole layer 92.

FIG. 5 is a cross-sectional view of a stage in the fabrication of atransducer similar to that shown in FIG. 3, the cross-section locatednear what will become the media-facing surface. A layer 98 of alumina orother insulating material has been formed by sputtering or other PVDatop the return pole layer 40. This layer 98 may be harder or softerthan alumina, and may be deposited in a single layer or in plurallayers, with a second of the plural layers being formed for example tofill in around an electroplated first recording layer 90, not shown inthis figure. The recording pole layer 92 was deposited by PVD oninsulating layer 98 and wear resistant material layer 102 deposited onlayer 92. A mask 104 of photoresist or the like was formed over layer102 to a width larger than that desired for pole tip 94. Directedetching such as IBE can then be performed to remove parts of layers 92and 102 not covered by the mask 104, leaving pole tip 94 covered by acap layer 55 of hard layer 102. The etching can also remove part oflayer 98 that is not covered by the mask, for example leaving a hardinsulating material adjacent a leading edge of pole tip 94 and having awidth corresponding to that of the pole tip 94.

After additional layers have been deposited the wafer is cut intoindividual die, one of the die cuts being substantially parallel to thecross-section shown, which is then polished so that hard layer 55 andpole tip 94 protrude slightly. Alternatively, a lift off mask can beformed over recording pole layer 92, leaving a opening over the desiredlocation for pole tip 94 through which a mask of physically hardmaterial is deposited, after which the lift off mask is removed. Thephysically hard material mask can then be used to protect pole tip 94during IBE or other directional etching of other parts of layer 92.

FIG. 6 is a cross-sectional view of a later step in the fabrication of atransducer similar to that shown in FIG. 5, in which a write pole tip114 is formed with a trapezoidal shape. Although the mask 104 of FIG. 5can be used for this purpose, a bilayer mask 144 is shown in thisexample to facilitate later refill of material around pole tip 114.After directional etching such as IBE or RIE has created a pole tipsimilar to pole tip 94 of FIG. 5, the etching is angled as indicated byarrows 150 to create the angled walls of pole tip 114. Creating a poletip 114 with a trailing edge of that is longer than a leading edge hasadvantages in avoiding side writing, particularly when the trailing edgeis also closer than the leading edge to the recording medium.

FIG. 7 is a cross-sectional view of a later step in the fabrication of atransducer of FIG. 6, in which nonmagnetic, electrically insulatingmaterial 124 such as alumina has been formed around pole tip 114 andatop mask 144.

FIG. 8 is a cross-sectional view of a later step in the fabrication of atransducer of FIG. 7, in which mask 144 has been lifted off and anotherpole tip 134 has been formed that is separated from the write pole tip94 by physically hard layer 55. Pole tip 134 can be part of a returnpole layer or an auxiliary pole layer that is formed in addition to thereturn pole layer, depending upon factors such as the size of pole tip134 and hard layer 102. Pole tip 134 can be part of a single pole layerthat curves over coils or can be a pedestal that is stitched to a longerpole layer.

FIG. 9 is a cross-sectional view of an embodiment in which pole tip 134is a pedestal that is magnetically coupled to an auxiliary pole layer123. An additional layer 123 of physically hard material may optionallybe formed between pedestal 134 and pole layer 123, although thecombination of layers 123 and 134 may be thought of as the auxiliarypole layer.

FIG. 10 is a cross-sectional view of an embodiment in which pole layer123 acts as a return pole layer that curves over coils 52 to terminatein pole tip 134. An additional layer 122 of physically hard material mayoptionally be formed along the trailing edge of pole layer 133.

1. A transducer for recording information on a perpendicular recordingmedium, the transducer comprising: a body having a leading end, atrailing end, and a medium-facing surface; a first soft magnetic layerdisposed in the body and terminating at a first pole tip disposedadjacent to the medium-facing surface; a second soft magnetic layer thatis magnetically coupled to the first soft magnetic layer in a part ofthe body distal to the medium-facing surface, the second soft magneticlayer terminating at a second pole tip disposed adjacent to themedium-facing surface, the second pole tip having a leading edge and atrailing edge, such that the leading edge is closer than the trailingedge to the leading end, and the trailing edge protrudes toward themedium, compared to the leading edge; and a nonmagnetic layer thatadjoins the trailing edge and does not coat the medium-facing surface.2. The transducer of claim 1, wherein the nonmagnetic layer has athickness that is in a range between about one hundred Angstroms andabout one micron.
 3. The transducer of claim 1, wherein the trailingedge is longer than the leading edge.
 4. The transducer of claim 1,wherein the second pole tip has a substantially trapezoidal shape. 5.The transducer of claim 1, wherein the second pole tip is separated fromthe first pole tip by the nonmagnetic layer.
 6. The transducer of claim1, wherein the first pole tip has an area that is at least two orders ofmagnitude greater than that of the second pole tip.
 7. A transducer forrecording information on a relatively-moving medium, the transducercomprising: a body having a leading end, a trailing end, and amedium-facing surface; a first soft magnetic layer disposed in the bodyand terminating at a first pole tip disposed adjacent to themedium-facing surface, the first soft magnetic layer having a leadingside and a trailing side, such that the leading side is closer than thetrailing side to the leading end, the leading side meeting the firstpole tip at an acute corner; a second soft magnetic layer that ismagnetically coupled to the first soft magnetic layer in a part of thebody distal to the media-facing surface, the second soft magnetic layerterminating at a second pole tip disposed adjacent to the medium-facingsurface, the second pole tip having a leading edge and a trailing edge,such that the leading edge is closer than the trailing edge to theleading end; and a nonmagnetic layer adjoining the trailing edge.
 8. Thetransducer of claim 7, wherein the nonmagnetic layer has a thicknessthat is in a range between about one hundred Angstroms and about onemicron.
 9. The transducer of claim 7, wherein the trailing edge iscloser than the leading edge to the medium.
 10. The transducer of claim7, wherein the trailing edge is longer than the leading edge.
 11. Thetransducer of claim 7, wherein the second pole tip has a substantiallytrapezoidal shape.
 12. The transducer of claim 7, wherein the secondpole tip is separated from the first pole tip by the nonmagnetic layer.13. The transducer of claim 7, wherein the first pole tip has an areathat is at least two orders of magnitude greater than that of the secondpole tip.
 14. The transducer of claim 7, wherein the second pole layerhas a trailing side that forms an acute angle with the second pole tipalong the trailing edge.
 15. A transducer for recording information on arelatively-moving medium, the transducer comprising: a body having aleading end, a trailing end, and a medium-facing surface; a first softmagnetic layer disposed in the body and terminating at a first pole tipdisposed adjacent to the medium-facing surface; a second soft magneticlayer that is magnetically coupled to the first soft magnetic layer in apart of the body distal to the media-facing surface, the second softmagnetic layer terminating at a second pole tip disposed adjacent to themedium-facing surface, the second pole tip having a leading edge and atrailing edge, such that the leading edge is closer than the trailingedge to the leading end, the trailing edge meeting the second pole tipat an acute corner; and a nonmagnetic layer adjoining the trailing edge.16. The transducer of claim 15, wherein the nonmagnetic layer has athickness that is in a range between about one hundred Angstroms andabout one micron.
 17. The transducer of claim 15, wherein the trailingedge is closer than the leading edge to the medium.
 18. The transducerof claim 15, wherein the trailing edge is longer than the leading edge.19. The transducer of claim 15, wherein the second pole tip has asubstantially trapezoidal shape.
 20. The transducer of claim 15, whereinthe second pole tip is separated from the first pole tip by thenonmagnetic layer.
 21. The transducer of claim 15, wherein the firstpole tip has an area that is at least two orders of magnitude greaterthan that of the second pole tip.